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Karyotype and evolution of the Tropidurus nanuzae species group (Sauria, Iguanidae)

Sanae Kasahara^I; Yatiyo Yonenaga-Yassuda^II; Miguel Trefaut Rodrigues^III

^IDepartamento de Biologia, Instituto de Biociências, UNESP, Caixa Postal 178, 13500 Rio Claro, SP, Brasil. Send correspondence to S.K.
^IIDepartamento de Biologia, Instituto de Biociências, USP, Caixa Postal 11461, 05499 Sao Paulo, SP, Brasil
^IIIDepartamento de Zoologia, Instituto de Biociências, USP, Caixa Postal 20520, 01498 Silo Paulo

ABSTRACT

The karyotypes of Tropidurus nanuzae, T. amathites and T. divaricatus, which form the nanuzae group, are presented. Data were obtained by Giemsa and NOR staining, C-banding and R-banding after in vivo treatment with 5-bromodeoxyuridine (BrdU). All females have 2n = 36 with 12 metacentric or submetacentric macrochromosomes and 24 microchromosomes, while males have 2n = 35. The mechanism of sex determination is of the XXAA:XAY/A type. The only chromosome difference among these species is related to the position of a secondary constriction and to the NOR localization on macrochromosome pair 6, as the result of a pericentric inversion. These data support the idea of monophyly in the species of the nanuzae group. Morphological and ecological evidence indicates that allopatric speciation is the most likely explanation for the differentiation of T. amathites and T. divaricatus, and the cytogenetic data support this mode of speciation.

Keywords: karyotype; evolution; Tropidurus nanuzae.

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